Integrated schottky diode phase change memory device

Abstract

A non-volatile memory structure can include phase change memory comprising a phase change material. The non-volatile memory structure can include a Schottky diode in series with the phase change memory, where a Schottky barrier of the Schottky diode is a surface of the phase change memory. This can be achieved by a suitable selection of material for the contact to the phase change memory. This can result in an integrated diode-memory structure that can control the directionality of current without adversely affecting the footprint of the structure.

Description

Background Technology

[0001] This invention relates to non-volatile memory, and more specifically, to memristive devices for neuromorphic computing.

[0002] "Machine learning" is used broadly to describe the primary functions of electronic systems that learn from data. In accelerated machine learning and cognitive science, artificial neural networks (ANNs) are a family of statistical learning models inspired by the biological neural networks of animals, particularly the brain. ANNs can be used to estimate or approximate the functions of systems that depend on a large number of inputs and are often unknown. ANN structures, neuromorphic microchips, and ultra-high-density non-volatile memories can be formed from high-density, low-cost circuit structures called cross-bar arrays. A basic cross-bar array configuration includes a set of conductive row lines and a set of conductive column lines formed to cross the set of conductive row lines. The crossings between the two sets of wires are separated by so-called cross-point devices, which can be formed from thin-film materials. Cross-point devices can be implemented as so-called memristor devices. Characteristics of memristor devices include non-volatility, the ability to store variable resistance values, and the ability to adjust the resistance up or down using current or voltage pulses. Summary of the Invention

[0003] A non-volatile memory structure may include a phase-change memory (PCM) comprising a phase-change material. The non-volatile memory structure may include a Schottky diode connected in series with the PCM, wherein the Schottky barrier of the Schottky diode is the surface of the PCM. This can produce an integrated diode-memory structure that allows control of current directionality without adversely affecting the structure's footprint.

[0004] The non-volatile memory structure in paragraph

[0003] can have the Schottky barrier serving as the interface between the phase change material and the contact. This can produce an integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0005] The non-volatile memory structure in paragraph

[0004] may have selective contacts with a work function 0.3-1 eV lower than that of the phase change material. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0006] The non-volatile memory structure in paragraph

[0004] may have selected contacts made of materials selected from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0007] The non-volatile memory structure in paragraph

[0004] may have selective contacts with a work function 0.3-1 eV higher than that of the phase change material. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0008] The non-volatile memory structure in paragraph

[0004] may have selective contacts made of a material selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0009] A non-volatile memory structure may include a phase-change material located between a first contact and a second contact, wherein the first and second contacts are made of different materials. This can produce an integrated diode-memory structure that allows control of the directionality of current without adversely affecting the structure's footprint.

[0010] The non-volatile memory structure in paragraph

[0009] can have the Schottky barrier serving as the interface between the phase change material and the contact. This can produce an integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0011] The non-volatile memory structure in paragraph

[0010] can be selected using contacts made of materials with a work function 0.3-1 eV lower than that of the phase change material. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0012] The non-volatile memory structure in paragraph

[0010] can be selected to have contacts made of materials chosen from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0013] The non-volatile memory structure in paragraph

[0010] can be selected using contacts made of materials with a work function 0.3-1 eV higher than that of the phase change material. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0014] The non-volatile memory structure in paragraph

[0010] can have selective contacts made of materials selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0015] A non-volatile memory structure may include multiple bit lines and multiple word lines. A PCM memory structure is located between the multiple bit lines and the multiple word lines. The PCM memory structure may include a phase-change material located between a first contact and a second contact. The first and second contacts are made of different materials. This can produce an integrated diode-memory structure that allows control of current directionality without adversely affecting the structure's footprint.

[0016] The non-volatile memory structure in paragraph

[0015] can have a Schottky barrier as the interface between the phase change material and the contact. This can produce an integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0017] The non-volatile memory structure in paragraph

[0016] can be selected using contacts made of materials with a work function 0.3-1 eV lower than that of the phase change material. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0018] The non-volatile memory structure in paragraph

[0016] can be selected to have contacts made of materials chosen from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0019] The non-volatile memory structure in paragraph

[0016] can be selected using contacts made of materials with a work function 0.3-1 eV higher than that of the phase change material. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0020] The non-volatile memory structure in paragraph

[0016] can have selective contacts made of materials selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0021] A non-volatile memory structure may include multiple bit lines and multiple word lines. A PCM memory structure is located between the multiple bit lines and the multiple word lines. The PCM memory structure may include a phase-change material and a Schottky diode connected in series with the phase-change memory. The Schottky barrier of the Schottky diode is the surface of the phase-change memory. The Schottky barrier is the interface between the phase-change material and the contact. This can produce an integrated diode-memory structure that can control the directionality of current without adversely affecting the structure's footprint.

[0022] The non-volatile memory structure in paragraph

[0021] can have a Schottky barrier serving as the interface between the phase change material and the contact. This can produce an integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0023] The non-volatile memory structure in paragraph

[0021] may have selective contacts with a work function lower than that of the phase change material (0.3-1 eV). This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0024] The non-volatile memory structure in paragraph

[0021] may have selected contacts made of a material selected from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can produce a p-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0025] The non-volatile memory structure in paragraph

[0021] may have selective contacts with a work function 0.3-1 eV higher than that of the phase change material. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure.

[0026] The non-volatile memory structure in paragraph

[0021] may have selected contacts made of a material selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can produce an n-type integrated diode-memory structure that can control the directionality of the current without adversely affecting the area occupied by the structure. Attached Figure Description

[0027] Figure 1 An arrangement of the intersection array according to an example embodiment is shown;

[0028] Figure 2 An electrical diagram illustrating the current flow path through an array of intersections according to an example embodiment is shown;

[0029] Figure 3An electrical diagram of an integrated Schottky PCM unit according to an example embodiment is shown;

[0030] Figure 4 An electrical diagram of an integrated Schottky PCM mushroom cell according to an example embodiment is shown;

[0031] Figure 5 An electrical diagram of an integrated Schottky PCM confined cell according to an example embodiment is shown;

[0032] Figure 6 An electrical diagram of an integrated Schottky PCM bridge cell according to an example embodiment is shown; and

[0033] The elements in the accompanying drawings are not necessarily drawn to scale and are not intended to depict specific parameters of the invention. For clarity and ease of illustration, the dimensions of elements may be exaggerated. Precise dimensions should be obtained by referring to the detailed description. The drawings are intended only to illustrate typical embodiments of the invention and should not be considered as limiting the scope of the invention. In the drawings, the same reference numerals denote the same elements. Detailed Implementation

[0034] Exemplary embodiments will now be described more fully herein with reference to the accompanying drawings, in which exemplary embodiments are illustrated. However, this disclosure may be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to make this disclosure thorough and complete, and to convey the scope of this disclosure to those skilled in the art. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments.

[0035] For the purposes described below, terms such as “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” and their derivatives should be referenced to the disclosed structures and methods oriented as shown in the accompanying drawings. Terms such as “above,” “cover,” “on top,” “on top,” “located,” or “located on top” mean that a first element (such as a first structure) is present on a second element (such as a second structure), wherein an intermediate element (such as an interface structure) may be present between the first and second elements. The term “direct contact” means that the first element (e.g., the first structure) and the second element (e.g., the second structure) are connected at the interface of the two elements without any intermediate conductive, insulating, or semiconductor layer.

[0036] To avoid obscuring the presentation of embodiments of the present invention, some processing steps or operations known in the art may be combined for presentation and illustrative purposes in the following detailed description, and may not be described in detail in some instances. In other instances, some processing steps or operations known in the art may not be described at all. It should be understood that the following description focuses more on the distinguishing features or elements of various embodiments of the present invention.

[0037] Analog computing uses memory devices such as memristors, which store information as the conductance range of the memory device. Typically, such memory devices are arranged in a cross-point array with multiple word lines and bit lines arranged in a grid pattern, where a single memory device can be read at a time when current is allowed to flow through the word lines and bit lines. For example, Figure 1 A simplified cross-point array is shown, comprising a first word line 10A, a second word line 10B, a first storage device 20A, a second storage device 20B, a third storage device 20C, a fourth storage device 20D, a first bit line 30A, and a second bit line 30B. Figure 1 In the example depicted, the desired read path P1 of the fourth memory device 20D is shown. However, during the read state of the fourth memory device 20D, there may be a sneak path P2 through the first memory device 20A, the second memory device 20B, and the third memory device 20C. Figure 2 The diagram shows a combination of read path P1 and latent path P2, wherein a first conductance G of the first memory device 20A is present. A The second conductance G of the second memory device 20B B The third conductance G of the third memory device 20C C and the fourth conductance G of the fourth memory device 20D D Therefore, in Figure 1 In the example layout depicted, instead of reading the state of the memory of the fourth memory device 20D as the fourth conductance G, D This state is replaced by the fourth conductance G. D The first conductance G of the combined first memory device 20A A The second conductance G of the second memory device 20B B The third conductance G of the third memory device 20C C From the equation This is a concern in traditional PCM memory applications, but it intensifies when the depicted crosspoint array is used for analog computation, where each memory device represents a series of values ​​(i.e., analog) rather than discrete values ​​(i.e., digital), because accurate readings of the conductance of each memory device are necessary for proper downstream computation.

[0038] Diodes can be used to limit the direction of current through a memory device, eliminating latent path P2 (e.g., removing the reverse path through the first memory device 20A). However, conventional diode designs impose additional considerations on space and processing, making them expensive. The structures included in this application present an integrated Schottky diode and PCM structure. As understood in this application, the phase change material of the PCM can behave like a semiconductor, allowing the surface of the phase change material to act as a Schottky barrier when a suitable diode contact material is selected for contact on only one of the surfaces of the phase change material. For example, for a p-type structure, the diode contact material may include a material having a work function lower than the barrier height of the phase change material, and in some embodiments, may be selected to have a work function 0.3-1 eV lower than the phase change material. In an n-type structure, for example, the diode contact material may include a material having a work function higher than the barrier height of the phase change material, and in some embodiments, may be selected to have a work function 0.3-1 eV higher than the phase change material.

[0039] Figure 3 A cross-sectional view of an integrated diode phase-change memory structure according to an example embodiment is shown. The material stack includes a bottom electrode 110, a top electrode 120, a phase-change material 130, and an interlayer dielectric (ILD) 140.

[0040] ILD 140 can be used to isolate this integrated diode memory cell. Suitable ILD materials include, but are not limited to, low-κ oxide materials, such as silicon oxide (SiOx), SiOCH, and / or ultra-low-κ oxide interlayer dielectric (ULK-ILD) materials, for example, having a dielectric constant κ of less than 2.7. For comparison, silicon dioxide (SiO2) has a dielectric constant κ value of 3.9. Suitable ultra-low-κ dielectric materials include (but are not limited to) porous organosilicon glass (pSiCOH).

[0041] According to one exemplary embodiment, phase change material 130 may be located above bottom electrode 110. Phase change material 130 may include materials that can be programmed to an amorphous (high resistance) or crystalline (low resistance) state by applying heat, such as chalcogenide-based materials. Examples of chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. Phase change materials may include Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloys. Alternatively, other suitable materials for phase change materials include Si-Sb-Te (silicon-antimony-tellurium) alloys, Ga-Sb-Te (gallium-antimony-tellurium) alloys, Ge-Bi-Te (germanium-bismuth-tellurium) alloys, In-Se (indium-tellurium) alloys, As-Sb-Te (arsenic-antimony-tellurium) alloys, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, and combinations thereof. In some embodiments, the phase change material may further include nitrogen, carbon, and / or oxygen. In some embodiments, the phase change material may be doped with a dielectric material, including but not limited to aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc.

[0042] The bottom electrode 110 and top electrode 120 are selected in such a way as to generate a Schottky barrier with the surface of the phase change material 130. For this purpose, the bottom electrode 110 and top electrode 120 are selected such that one may comprise a low-resistance metal, while the other is formed of a contact diode material. The low-resistance metal may be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material may be selected based on whether the PCM device is an n-type or p-type device. For p-type devices, the diode contact material may comprise a material having a work function lower than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV lower than that of the phase change material. For the aforementioned PCM material, such a diode contact material may be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For n-type devices, the diode contact material may comprise a material having a work function higher than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV higher than that of the phase change material. For the aforementioned PCM material, such material can be, for example, molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0043] As previously described, the bottom electrode 110 and the top electrode 120 are made of different contact materials so that the Schottky barrier formed at the interface between the electrode made of diode contact material and the phase change material 130 can be used as a Schottky diode. Thus, in one example, the bottom electrode 110 is a low-resistance metal, and the top electrode 120 is a diode contact material. Therefore, in another example, the top electrode 120 is a low-resistance metal, and the bottom electrode 110 is a diode contact material. It should be noted that while the bottom electrode 110 and the top electrode 120 may be layers and materials separate from the word lines and bit lines attached to said electrodes, or may not be clearly distinguishable from the word lines and bit lines to which they are attached (e.g., the word lines or bit lines may be diode contact materials and / or low-resistance metals).

[0044] Figure 4 A cross-sectional view is depicted of an integrated diode mushroom cell phase-change memory structure according to an exemplary embodiment. The material stack includes a bottom electrode 210, a top electrode 220, a phase-change material 230, a PCM heater 231, a PCM dielectric 232, and an interlayer dielectric (ILD) 240.

[0045] ILD 240 can be used to isolate this integrated diode memory cell. Suitable ILD materials include, but are not limited to, low-κ oxide materials, such as silicon oxide (SiOx), SiOCH, and / or ultra-low-κ oxide interlayer dielectric (ULK-ILD) materials, for example, having a dielectric constant κ of less than 2.7. In contrast, silicon dioxide (SiO2) has a dielectric constant κ value of 3.9. Suitable ultra-low-κ dielectric materials include (but are not limited to) porous organosilicon glass (pSiCOH).

[0046] The PCM dielectric 232 may be selected to withstand heating caused by the PCM heater 231 to change the state of the phase change material 230. The PCM dielectric may include, but is not limited to, low-κ oxide materials, such as silicon oxide (SiOx).

[0047] According to one embodiment, the phase change material 230 may be located above the PCM heater 231. The phase change material 230 may include a material that can be programmable to an amorphous (high resistance) state or a crystalline (low resistance) state by applying heat, such as chalcogenide-based materials. Examples of chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. The phase change material may include a Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloy. Alternatively, other suitable materials for phase change materials include Si-Sb-Te (silicon-antimony-tellurium) alloys, Ga-Sb-Te (gallium-antimony-tellurium) alloys, Ge-Bi-Te (germanium-bismuth-tellurium) alloys, In-Se (indium-tellurium) alloys, As-Sb-Te (arsenic-antimony-tellurium) alloys, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, and combinations thereof. In some embodiments, the phase change material may further include nitrogen, carbon, and / or oxygen. In some embodiments, the phase change material may be doped with a dielectric material, including but not limited to aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc.

[0048] The PCM heater 231 and top electrode 220 are selected in such a way as to generate a Schottky barrier with the surface of the phase change material 230. For this purpose, the PCM heater 231 and top electrode 220 are selected such that one may comprise a low-resistance metal, while the other is formed of a contact diode material. The low-resistance metal may be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material may be selected based on whether the PCM device is an n-type or p-type device. For p-type devices, the diode contact material may comprise a material having a work function lower than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV lower than that of the phase change material. For the aforementioned PCM material, such a diode contact material may be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For n-type devices, the diode contact material may comprise a material having a work function higher than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV higher than that of the phase change material. For the aforementioned PCM material, such material can be, for example, molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0049] As previously described, the PCM heater 231 and the top electrode 220 are made of different contact materials, so that the Schottky barrier formed at the interface between the electrode made of diode contact material and the phase change material 230 can be used as a Schottky diode. Therefore, in one example, the PCM heater 231 is a low-resistance metal and the top electrode 220 is a diode contact material. Therefore, in another example, the top electrode 220 is a low-resistance metal and the PCM heater 231 is a diode contact material.

[0050] The bottom electrode 210 may be made of a low-resistance metal, such as Al, W, Cu, TiN, TaN, or other suitable materials. It should be noted that although the bottom electrode 210 and the top electrode 220 may be layers and materials separate from the word lines and bit lines attached to the electrodes, or they may not be clearly distinguishable from the word lines and bit lines to which they are attached (e.g., the word lines or bit lines may be diode contact materials and / or low-resistance metals).

[0051] Figure 5 A cross-sectional view is depicted of an integrated diode mushroom cell phase-change memory structure according to an exemplary embodiment. The material stack includes a bottom electrode 310, a top electrode 320, a phase-change material 330, a pad 331, a PCM dielectric 332, and an interlayer dielectric (ILD) 340.

[0052] ILD 340 can be used to isolate this integrated diode memory cell. Suitable ILD materials include, but are not limited to, low-κ oxide materials, such as silicon oxide (SiOx), SiOCH, and / or ultra-low-κ oxide interlayer dielectric (ULK-ILD) materials, for example, having a dielectric constant κ of less than 3.7. In contrast, silicon dioxide (SiO2) has a dielectric constant κ value of 3.9. Suitable ultra-low-κ dielectric materials include (but are not limited to) porous organosilicon glass (pSiCOH).

[0053] The PCM dielectric 332 can be selected to withstand heating caused by the PCM heater (liner) 331 to change the state of the phase change material 330. The PCM dielectric can be, but is not limited to, low-κ oxide materials, such as silicon oxide (SiOx).

[0054] According to an example embodiment, phase change material 330 may be located above PCM heater (liner) 331. Phase change material 330 may include materials that can be programmable to an amorphous (high resistance) or crystalline (low resistance) state by applying heat, such as chalcogenide-based materials. Examples of chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. Phase change materials may include Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloys. Alternatively, other suitable materials for phase change materials include Si-Sb-Te (silicon-antimony-tellurium) alloys, Ga-Sb-Te (gallium-antimony-tellurium) alloys, Ge-Bi-Te (germanium-bismuth-tellurium) alloys, In-Se (indium-tellurium) alloys, As-Sb-Te (arsenic-antimony-tellurium) alloys, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, and combinations thereof. In some embodiments, the phase change material may further include nitrogen, carbon, and / or oxygen. In some embodiments, the phase change material may be doped with a dielectric material, including but not limited to aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc.

[0055] The top electrode 320 and the pad 331 or bottom electrode 310 are selected in such a way as to generate a Schottky barrier with the surface of the phase change material 330. To do this, the top electrode 320 and the pad 331 or bottom electrode 310 are selected such that one may comprise a low-resistance metal, while the other is formed of a contact diode material. The low-resistance metal may be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material may be selected based on whether the PCM device is an n-type or p-type device. For p-type devices, the diode contact material may comprise a material having a work function lower than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV lower than the phase change material. For the aforementioned PCM material, such a diode contact material may be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For n-type devices, the diode contact material may comprise a material having a work function higher than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV higher than the phase change material. For the aforementioned PCM material, such material can be, for example, molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0056] As previously described, the top electrode 320 and the pad 331 or bottom electrode 310 are different contact materials so that the Schottky barrier formed at the interface between the electrode made of diode contact material and the phase change material 330 can be used as a Schottky diode. Therefore, in one example, the pad 331 is a low-resistance metal, while the top electrode 320 is a diode contact material. Thus, in another example, the top electrode 320 is a low-resistance metal, and the pad 331 is a diode contact material.

[0057] The bottom electrode 310 may be made of a low-resistance metal, such as Al, W, Cu, TiN, TaN, or other suitable materials. It should be noted that while the bottom electrode 310 and the top electrode 320 may be layers and materials separate from the word lines and bit lines attached to the electrodes, they may also be indistinguishable from the word lines and bit lines to which they are attached (e.g., the word lines or bit lines may be diode contact materials and / or low-resistance metals).

[0058] Figure 6 A cross-sectional view of an integrated diode phase-change memory structure according to an example embodiment is shown. The material stack includes a first electrode 410, a second electrode 420, a phase-change material 430, and an interlayer dielectric (ILD) 440.

[0059] ILD 440 can be used to isolate this integrated diode memory cell. Suitable ILD materials include, but are not limited to, low-κ oxide materials, such as silicon oxide (SiOx), SiOCH, and / or ultra-low-κ oxide interlayer dielectric (ULK-ILD) materials, for example, having a dielectric constant κ of less than 2.7. In contrast, silicon dioxide (SiO2) has a dielectric constant κ value of 3.9. Suitable ultra-low-κ dielectric materials include (but are not limited to) porous organosilicon glass (pSiCOH).

[0060] According to one exemplary embodiment, phase change material 430 may be located above the first electrode 410. Phase change material 430 may include a material that can be programmable to an amorphous (high resistance) state or a crystalline (low resistance) state by applying heat, such as chalcogenide-based materials. Examples of chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. Phase change materials may include Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloys. Alternatively, other suitable materials for phase change materials include Si-Sb-Te (silicon-antimony-tellurium) alloys, Ga-Sb-Te (gallium-antimony-tellurium) alloys, Ge-Bi-Te (germanium-bismuth-tellurium) alloys, In-Se (indium-tellurium) alloys, As-Sb-Te (arsenic-antimony-tellurium) alloys, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, and combinations thereof. In some embodiments, the phase change material may further include nitrogen, carbon, and / or oxygen. In some embodiments, the phase change material may be doped with a dielectric material, including but not limited to aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc.

[0061] The first electrode 410 and the second electrode 420 are selected in such a way as to generate a Schottky barrier with the surface of the phase change material 430. To do this, the first electrode 410 and the second electrode 420 are selected such that one may comprise a low-resistance metal, while the other is formed of a contact diode material. The low-resistance metal may be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material may be selected based on whether the PCM device is an n-type or p-type device. For p-type devices, the diode contact material may comprise a material having a work function lower than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV lower than that of the phase change material. For the aforementioned PCM material, such a diode contact material may be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For n-type devices, the diode contact material may comprise a material having a work function higher than the barrier height of the phase change material, and in some embodiments, it may be selected to have a work function 0.3-1 eV higher than that of the phase change material. For the aforementioned PCM materials, such materials can be, for example, Mo, TiN, W, Au, Co, Cu, Ni, Pd, Ir, or other suitable materials.

[0062] As previously described, the first electrode 410 and the second electrode 420 are made of different contact materials so that the Schottky barrier formed at the interface between the electrode made of diode contact material and the phase change material 430 can be used as a Schottky diode. Thus, in one example, the first electrode 410 is a low-resistance metal and the second electrode 420 is a diode contact material. Therefore, in another example, the second electrode 420 is a low-resistance metal and the first electrode 410 is a diode contact material. It should be noted that while the first electrode 410 and the second electrode 420 may be layers and materials separate from the word lines and bit lines attached to the electrodes, they may also be indistinguishable from the word lines and bit lines to which they are attached (e.g., the word lines or bit lines may be diode contact materials and / or low-resistance metals).

[0063] Various embodiments of the invention have been described for illustrative purposes, but are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope of the described embodiments. The terminology used herein has been chosen to best explain the principles of the embodiments, their practical application, or improvements to existing technologies in the market, or to enable others skilled in the art to understand the embodiments disclosed herein. Therefore, the invention is not limited to the precise forms and details described and illustrated, but falls within the scope of the appended claims.

[0064] In a preferred embodiment of the present invention, a non-volatile memory structure is now provided, comprising: a phase-change memory (PCM) including a phase-change material; and a Schottky diode connected in series with the PCM, wherein the Schottky barrier of the Schottky diode is the surface of the PCM. Preferably, the Schottky barrier is the interface between the PCM and a contact. The work function of the contact material is preferably 0.3-1 eV lower than that of the PCM. The contact material may be selected from the group consisting of titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. Preferably, the work function of the contact material is 0.3-1 eV higher than that of the PCM. The contact material may be selected from the group consisting of molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0065] In another preferred embodiment of the present invention, a non-volatile memory structure is provided, comprising: a plurality of bit lines and a plurality of word lines, wherein a PCM memory structure is located between the plurality of bit lines and the plurality of word lines; and wherein the PCM memory structure comprises a phase change material and a Schottky diode connected in series with the PCM memory, wherein the Schottky barrier is the interface between the phase change material and the contact. Preferably, the work function of the contact material is 0.3-1 eV lower than the work function of the phase change material. Preferably, the work function of the contact material is 0.3-1 eV higher than the work function of the phase change material.

Claims

1. A non-volatile memory structure, comprising: Phase change memory, which contains phase change materials; The first electrode is in direct contact with the first surface of the phase change material; The PCM heater is in direct contact with the second surface of the phase change material, wherein the second surface of the phase change material is opposite to the first surface of the phase change material; The work function of the material in the PCM heater is less than that of the phase change material.

2. The structure according to claim 1, wherein the interface between the phase change material and the PCM heater is a Schottky barrier.

3. The structure according to claim 1, wherein the work function of the material of the PCM heater is 0.3 eV to 1 eV lower than the work function of the phase change material.

4. The structure according to claim 1, wherein the material of the first electrode is selected from the group consisting of aluminum, tungsten, copper, titanium nitride, and tantalum nitride, and The material of the PCM heater is selected from the group consisting of molybdenum, tantalum, tungsten, manganese, zirconium, and hafnium.

5. The structure according to claim 1, wherein the width of the phase change material is equal to or less than the width of the first electrode.

6. The structure according to claim 1, wherein the material of the first electrode is selected from the group consisting of aluminum, tungsten, copper, titanium nitride, and tantalum nitride, and The material of the PCM heater is selected from the group consisting of molybdenum, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

7. The structure according to claim 1, wherein the material of the first electrode is selected from the group consisting of aluminum, tungsten, and copper, and The material of the PCM heater is selected from the group consisting of zirconium, hafnium, nickel, palladium and iridium.

8. The structure according to claim 1 further includes a second electrode, the second electrode being in direct contact with the PCM heater, wherein the first electrode and the second electrode are made of a first material, and the PCM heater is made of a second material, wherein the first material is different from the second material.

9. A non-volatile memory structure, comprising: Phase change memory, which contains phase change materials; The top electrode is in direct contact with the top surface of the phase change material; The lining is in direct contact with the sidewalls and bottom surface of the phase change material; The bottom electrode is in direct contact with the bottommost surface of the liner; The work function of the lining material is less than that of the phase change material.

10. The structure according to claim 9, further comprising: Multiple bit lines and multiple word lines, wherein the phase-change memory is located between the multiple bit lines and the multiple word lines.

11. The structure according to claim 9, wherein the width of the phase change material is smaller than the width of the top electrode and smaller than the width of the bottom electrode.

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